If you cannot easily fix voltage drop in the hot side of the harness, one way around it is to cut the blue "ignition run" wire coming out of the bulkhead at some point BEFORE it branches off. Use the end coming out of the firewall to trigger a Bosch relay, power the relay through a breaker / fuse from the starter relay stud, and hook the other cut end of the blue "IGN1" to the switched contact on the relay. This will then provide a solid voltage referenced to the battery for underhood loads, including the VR